Takashi Hosoya

Takashi Hosoya
Kyoto Prefectural University · Graduate School of Life and Environmental Sciences

Doctor of Energy Science

About

65
Publications
10,390
Reads
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2,016
Citations
Additional affiliations
April 2018 - present
Kyoto Prefectural University
Position
  • Professor (Assistant)
April 2016 - March 2018
Kyoto Prefectural University
Position
  • Professor (Associate)
April 2011 - March 2016
University of Natural Resources and Life Sciences Vienna
Position
  • PostDoc Position
Description
  • Apr 2014- JSPS Postdoctoral Fellow for Research Abroad
Education
April 2005 - May 2008
Kyoto University
Field of study
  • Graduate School of Energy Science
April 2003 - March 2005
Kyoto University
Field of study
  • Graduate School of Energy Science
April 1999 - March 2003
Kyoto University
Field of study
  • Faculty of Agriculture

Publications

Publications (65)
Article
We have proposed plausible reaction pathways involved in the chemical conversion of softwood lignin to vanillin through alkaline aerobic oxidation.
Article
Alkaline aerobic oxidation is a promising way to convert lignin to low molecular weight phenols, especially 4-hydroxybenzaldehydes. Our previous studies reported that oxidation of softwood lignin samples with a bulky cation, Bu4N⁺, facilitates selective production of vanillin (4-hydroxy-3-methoxybenzaldehyde). This study presents vanillin productio...
Article
Furan compounds, especially 5-hydroxymethylfurfural (5-HMF) and furfural (FF), are promising platform chemicals that can be produced from various lignocellulosics. This study presents production of the furan compounds from moso bamboo (Phyllostachys edulis) in an ionic liquid, 1-methylimidazolium hydrogen sulfate ([HMIM]HSO4), which acts as both so...
Article
Full-text available
Chromophores, colored substances of rather high stability that reduce brightness, are present in all kinds of cellulosic products, such as pulp, fibers, aged cellulosic material, and even in very low concentrations in highly bleached pulps. Thus, they are the prime targets of industrial pulp bleaching. In this study, the three cellulosic key chromo...
Article
3,8-Bis(methoxymethoxy)benzo [b]xanthene-12-one (1a) was reacted with n-butyllithium at −78 °C to afford the expected 1,2-adduct 1b and also the 1,4-adduct 1c. Using 2-Me-THF as the solvent afforded predominantly the 1,2-adduct 1b in 66% yield and the 1,4-adduct 1c in 5% yield. In contrast, in THF, the 1,4-adduct 1c was obtained as the major produc...
Article
Intrasheet interaction of native cellulose was investigated at the MP2 and DFT(B3LYP) levels of theory, employing various one-sheet crystalline models. Our MP2//DFT(B3LYP) calculations for the smallest two dimensional dimeric system possessing a short O6-H···O3’ hydrogen bond and a long O6-H···O2’ one indicated that the interaction energy between t...
Article
Full-text available
Aerobic oxidation of native soft wood lignin in an aqueous solution of Bu4NOH facilitates efficient production of vanillin (4-hydroxy-3-methoxybenzaldehyde), which is one of the platform chemicals in industry. Oxidation of Japanese cedar (Cryptomeria japonica) wood flour at 120 °C for 4 h under O2 in Bu4NOH-based aqueous solutions produced vanillin...
Article
Full-text available
2,5-Dihydroxy-[1,4]-benzoquinone (DHBQ, 1) is the most prominent representative of cellulosic key chromophores, which occur almost ubiquitously in all types of aged cellulosics. The degradation of DHBQ by chlorine dioxide under conditions of industrial pulp bleaching (“D stage”) was studied, i.e. in moderately acidic medium (pH 3) at temperatures b...
Article
Full-text available
The chemistry of cellulosic key chromophores is challenging because of the usually very low concentration of the colored compounds in real-world cellulosic matrices. It offers many surprises and positive outcomes; unfortunately there are also pitfalls and disappointments. This report discusses eight examples or surprising chemistry out of the realm...
Article
Full-text available
Literature is strongly contradictory about the molecular reasons for yellowing and brightness reversion of pure (lignin- and hemicellulose-free) celluloses, such as in highly bleached pulps, bacterial cellulose, or cotton linters. While oxidized groups—carbonyls (CO) and carboxyls (COOH)—have been recognized as the initiators of yellowing, they are...
Article
Vanillin is one of the industrially important compounds that can be produced from lignin. This study presents production of vanillin and vanillic acid (oxidized form of vanillin) through aerobic oxidation of Japanese cedar (Cryptomeria japonica) at 120 °C for 72 h in aqueous alkali solutions with several Bu4N⁺ and OH⁻ concentrations (1.25, 2.50, an...
Article
Several ionic liquids promote depolymerization of wood components, i.e., polysaccharides and lignin, into low molecular weight compounds, some of which further re-polymerize into resin-like compounds. In this study, the depolymerization/re-polymerization of wood components in ionic liquids was applied to preparation of plywoods from Japanese cedar...
Article
Full-text available
5,8-Dihydroxy-[1,4]-naphthoquinone (DHNQ) is one of the key chromophores occurring in all types of aged cellulosics. This study investigates the degradation of DHNQ by chlorine dioxide at moderately acidic (pH 3) conditions, corresponding to the conditions of industrial bleaching (“D stage”). The degradation involves three major pathways. As initia...
Article
Full-text available
The dihydroxyacetophenones 2,5-dihydroxyacetophenone (2,5-DHAP) and 2,6-dihydroxy-acetophenone (2,6-DHAP) belong to the key chromophores in cellulosic materials. The pulp and paper industry targets these key chromophores in their bleaching sequences to obtain brighter products. 2,5-DHAP and 2,6-DHAP were degraded with hydrogen peroxide in alkaline...
Article
Full-text available
Depolymerization of cellulose starting from an oxidized anhydroglucose unit through β-alkoxy-elimination, triggered by alkaline media, is one of the key reactions responsible for cellulose aging. This study investigates the detailed mechanisms for the chain cleavage by a combination of experimental and quantum chemical methods. Three model compound...
Article
Full-text available
2,5-Dihydroxy-[1,4]-benzoquinone (DHBQ) and 5,8-dihydroxy-[1,4]-naphthoquinone (DHNQ) are two key chromophores which are almost ubiquitous in cellulosic materials. Their fate under conditions of alkaline peroxide bleaching (P stage) has been established previously, but the intermediacy of cyclic peroxides, which so far had only been postulated, rem...
Article
Full-text available
5-Hydroxymethylfurfural (5-HMF) from lignocellulosics has attracted attention as a platform chemical in chemical industry. In 5-HMF production processes, undesired degradation of 5-HMF by acid catalysts generally occurs, by which the 5-HMF yield is decreased along with formation of various types of by-products. In this study, we employed an acidic...
Article
The efficient conversion of lignin, a major component of lignocellulosics, to monomeric aromatics is a hot topic in biorefining. In this study, we developed a method for selective degradation of several types of lignin [milled wood lignin, sodium lignosulfonate, soda lignin, and Japanese cedar (Cryptomeria japonica) wood flour] in Bu4NOH·30H2O (mp...
Article
5,8-Dihydroxy-[1,4]-naphthoquinone (DHNQ) is one of the key chromophores in cellulosic materials. Its almost ubiquitous presence in cellulosics makes it a target molecule of the pulp and paper industry’s bleaching efforts. In the presented study, DHNQ was treated with hydrogen peroxide under alkaline conditions at pH 10, resembling the conditions o...
Article
Full-text available
Hexeneuronic acids (HexA) have long been known as triggers for discoloration processes in glucuronoxylan-containing cellulosic pulps. They are formed under the conditions of pulping from 4-O-methylglucuronic acid residues, and are removed in an “A stage” along the bleaching sequences, which mainly comprises acidic washing treatments. The chemical s...
Article
Full-text available
Hexeneuronic acids (HexA) are a major cause of discoloration (yellowing/brightness reversion) in pulps from xylan-containing wood, being generated from the xylan’s 4-O-methylglucuronic acid residues. The HexA-derived chromophores, whose identification and structure confirmation have been described in the previous part of this series (Rosenau et al....
Article
Full-text available
Hexeneuronic acid (HexA) is formed under pulping conditions from 4-O-methyl-glucuronic acid residues in xylans by methanol elimination. It is usually removed by an acidic washing treatment (A-stage) within the pulp bleaching sequence. Hexeneuronic acid has long been recognized as a source of color generation in pulps, but the chemical structure of...
Article
The 5-methyl group in 2-hydroxy-[1,4]-benzoquinone shows a peculiar reactivity that depends on the pH of the reaction medium. Under acidic conditions, ortho-quinone methide tautomers of the parent para-quinones are present in equilibrium. The 5-methylene group is stabilized by resonance, incorporating canonic structures with a positive charge at th...
Article
Full-text available
N-Methylmorpholine-N-oxide (NMMO) cannot be completely separated by extraction from mixtures with common 1,3-dialkylimidazolium ionic liquids (ILs) due to strong ionic interactions between the two components. At elevated temperatures, above approx. 90 °C, especially under dry conditions and in the presence of acid, alkylating or acylating agents, r...
Article
Full-text available
Studies of cellulose aging and yellowing that involved a 1,4-dimethyl 3-keto β-d-glucoside (compound 1) model of oxidized cellulose led to a hemi-hydrated crystal of title compound 2 (1,6-dihydroxy-3,8-bis-hydoxymethyl-5,10-dimethoxy-4,9-dioxa-tricyclo [5,3,1,1,2,6] dodecane-11,12-dione). The same compound 2 was isolated in low yield from “real-wor...
Article
A method for easy and fast regeneration of aqueous periodate solutions from dialdehyde cellulose (DAC) production by ozone treatment is presented, along with a direct and reliable simultaneous quantification of iodate and periodate by reversed-phase HPLC. The influence of iodate and ozone concentration, solution pH, and reaction time on the regener...
Article
Six-electron oxidation of hexahydroxybenzene C6(OH)6 leads to cyclohexanehexaone (CO)6 via two intermediates, tetrahydroxy-1,4-benzoquinone and rhodizonic acid (5,6-dihydroxycyclohex-5-ene-1,2,3,4-tetraone). All these quinoid compounds show a rich and colorful chemistry: formation of chromophoric metal complexes is a special feature of the compound...
Article
Ion pair formation from 2,3-di-O-methyl-4,6-O-formylidene-α-d-mannopyranosyl triflate αTMan and its d-glucopyranosyl counterpart αTGlc was investigated at the DFT(M06-2X) level of theory, for the purpose of clarifying the effects of the 4,6-tethering on the structure and stability of α- and β-contact ion pairs and solvent-separated ion pairs at -78...
Article
Full-text available
The chromophore release and identification method isolates well-defined chromophoric substances from different cellulosic matrices, such as highly bleached pulps, cotton linters, bacterial cellulose, viscose or lyocell fibers, and cellulose acetates. The chromophores are present only in extremely low (ppm to ppb) concentrations. The concept of prim...
Article
2,5-Dihydroxyacetophenone (DHAP) is one of the three key chromophores found in aged cellulosics. Knowledge of the general reactivity and chemistry of this compound is helpful for a better understanding of cellulose aging and yellowing as well as bleaching of cellulosic materials - processes which also have considerable economic importance. This pap...
Article
2,5-Dihydroxy-[1,4]-benzoquinone (DHBQ) is one of the key chromophores in cellulosics. Due to its special resonance stabilization, it is a prime survivor of bleaching treatments and its degradation is essential in pulp bleaching. The clarification of the degradation mechanism of this compound is indispensable for targeting improvements of pulp blea...
Article
The chemical nature of contact ion pairs and solvent-separated ion pairs from 2,3,4,6-tetra-O-methyl-α-D-mannopyranosyl triflate was investigated at the DFT(M06-2X) level of theory. Comparison of the present results to those obtained for the D-glucopyranosyl counterpart in our previous study indicated that the ion pairs from the D-mannopyranosyl tr...
Article
The thermal reactivities of some simple glycosides (methyl α- and β-D-glucopyranosides, methyl β-D-xylopyranoside and levoglucosan (1,6-anhydro-β-D-glucopyranose)) in aromatic substances were studied in closed ampoules. Under neat (molten) conditions (N2, 15 min), these glycosides decomposed completely over the temperature range 260–280 °C. These s...
Article
Glycoside formation in organic synthesis is believed to occur along a reaction path involving an activated glycosyl donor with a covalent bond between the glycosyl moiety and the leaving group, followed by formation of contact ion pairs with the glycosyl moiety loosely bound to the leaving group, and eventually solvent-separated ion pairs with the...
Conference Paper
Full-text available
2,5-Dihydroxy-[1,4]-benzoquinone (DHBQ) is one of the key chromophores occurring in all types of aged cellulosics. In the present work, we have addressed the molecular mechanisms of DHBQ degradation by hydrogen peroxide by a combination of synthesis, kinetic and computational approaches, attempting to provide a solid knowledge base for optimization...
Article
Levoglucosan (1,6-anhydro-β-D-glucopyranose) formation by the thermal degradation of native cellulose was investigated by MP4(SDQ)//DFT(B3LYP) and DFT(M06-2X)//DFT(B3LYP) level computations. The computational results of dimer models lead to the conclusion that the degradation occurs by a concerted mechanism similar to the degradation of methyl β-D-...
Chapter
Recent results support the assumption that hydroquinones (e.g., methoxyhydroquinone, MHQ), benzoquinones (e.g., methoxy-[1,4]benzoquinone, MBQ; 2,5-dihydroxy-[1,4]benzoquinone, DHBQ), and quinone imines (e.g., 2,5-dihydroxy-[1,4]benzoquinone imine, DHBQI) are pivotal compounds in the oxidative degradation of ligneous materials and in the formation...
Article
2,5-Dihydroxy-[1,4]-benzoquinone (DHBQ) is one of the key chromophores occurring in all types of aged cellulosics. This study investigates the mechanism of H2O2 degradation of DHBQ under conditions relevant to pulp bleaching (3.0% H2O2, NaOH , pH 10), to obtain insights useful for improved pulp processing. DHBQ is degraded quantitatively into malon...
Article
2,5-Dihydroxy-[1,4]-benzoquinone (DHBQ) is one of the key chromophores occurring in all types of aged cellulosics. This study investigates the mechanism of H2O2 degradation of DHBQ under conditions relevant to pulp bleaching (3.0% H2O2, NaOH , pH 10), to obtain insights useful for improved pulp processing. DHBQ is degraded quantitatively into malon...
Article
Full-text available
Ammoxidized technical lignins are valuable soil-improving materials that share many similarities with native terrestrial humic substances. In contrast to lignins, the chemical fate of carbohydrates as typical minor constituents of technical lignins during the ammoxidation processes has not been thoroughly investigated. Recently, we reported the for...
Article
Full-text available
5,8-Dihydroxy-[1,4]-naphthoquinone (DHNQ) is one of the key chromophores found in aged cellulosics. Cellulose aging and yellowing as well as bleaching of cellulosic materials are key processes in the pulp and paper industries and have considerable economic importance: the knowledge of the general reactivity and chemistry of this compound is thus he...
Article
Full-text available
2,5-Dihydroxy-[1,4]-benzoquinone is one of the three key chromophores found in aged cellulosics. Knowledge of the general reactivity and chemistry of this compound is helpful for a better understanding of cellulose aging and yellowing as well as bleaching of cellulosic materials - processes which also have considerable economic importance. This pap...
Article
One of the difficulties in application of the usual reference interaction site model self-consistent field (RISM-SCF) method to a highly polarized and bulky system arises from the approximate evaluation of electrostatic potential (ESP) with pure point charges. To improve this ESP evaluation, the ESP near a solute is directly calculated with a solut...
Article
2,5-Dihydroxy-1,4-benzoquinone (DHBQ) is one of the key chromophores formed upon aging in cellulosic materials. This study addresses the degradation mechanism of DHBQ by hydrogen peroxide to provide a solid knowledge base for optimization of bleaching sequences aiming at DHBQ removal. Kinetic analysis provided an activation energy (E(a)) of 20.4 kc...
Article
In hot-water molecular dynamics simulation at 370 K, four cellulose III_I crystal models, with different lattice planes and dimensions, exhibited partial crystalline transformations of (1 -1 0) chain sheets, in which hydroxymethyl groups were irreversibly rotated from gt into tg conformations, accompanied by hydrogen-bond exchange from the original...
Article
Degradation of anomeric phenyl d-glucosides to levoglucosan under basic condition is theoretically studied. MP4(SDQ)//DFT(B3LYP)-computational results indicate that the degradation of phenyl α-glucoside (R(α)) occurs via the S(N)icB mechanism. In this mechanism, the oxyanion at the C6, which is formed through deprotonation of the OH group, directly...
Article
Thermal conversion of methyl beta-d-glucoside to levoglucosan was studied with the MP4//DFT(B3LYP) method. The first step is conformational change of the reactant to (1)C(4) from (4)C(1). The second step is intramolecular nucleophilic substitution at the anomeric C1, which occurs via one step without oxacarbenium ion intermediate. The DeltaG(0)() v...
Article
Solid/liquid- and vapor-phase interactions between cellulose- and lignin (Japanese cedar milled wood lignin)-derived pyrolysis products were studied under the conditions of N2/600 °C/40–80 s. A dual-space closed ampoule reactor was used to eliminate the solid/liquid-phase interactions, and careful comparison of the resulting data with those of the...
Article
Although char formation from lignin is an important process in wood pyrolysis, the molecular mechanism has not been clarified yet. In this study, the vapor-phase char formation of various lignin-related compounds was studied under the pyrolysis conditions of N2/600°C/80s. The methoxyl groups were found necessary for char formation. Interestingly, e...
Article
Gasification reactivities of the cellulose- and lignin-derived primary tar and char fractions were evaluated under the pyrolysis conditions (N2/600°C/50–120s) with a closed ampoule reactor. The closed ampoule reactor allowed the precise setting of the residence time and quantitative recovery of the products. The primary tar fraction from cellulose...
Article
Influence of the amount of levoglucosan-loading on the pyrolysis behavior was studied in N2 at 400°C with a dual-space closed ampoule reactor. The results indicated that the pyrolytic pathways are different between vapor- and liquid/solid-phases. Relative contribution of these two pyrolysis conditions changed depending on the amount of levoglucosan...
Article
Secondary reactions of lignin-derived primary tar components were studied with a closed ampoule reactor under the conditions of N-2/600 degrees C/40-120 s. The tar fractions from Japanese cedar milled wood lignin and model compounds were characterized with the GPC, H-1 NMR and GC/MS analyses. Changes in the tar composition indicated the following p...
Article
Full-text available
Kyoto University (京都大学) 0048 新制・課程博士 博士(エネルギー科学) 甲第14068号 エネ博第177号 新制/エネ/41 UT51-2008-F460 2008-05-23 京都大学大学院エネルギー科学研究科エネルギー社会・環境科学専攻 (主査)教授 坂 志朗, 教授 東野 達, 准教授 河本 晴雄 学位規則第4条第1項該当
Article
The influence of inorganic matter on the pyrolysis of Japanese cedar (Cryptomeria japonica) wood was studied at a gasification temperature of 800°C with demineralization through acid washing. Some influences on the formation of char, tar, and low molecular weight products coincided with results reported at temperatures lower than the gasification t...
Article
Cellulose–hemicellulose and cellulose–lignin interactions during pyrolysis at gasification temperature (800 °C) were investigated with various cellulose samples mixed with hemicellulose (glucomannan or xylan) or milled wood lignin. Significant interactions were observed in cellulose–lignin pyrolysis; lignin inhibited the thermal polymerization of l...
Article
Thermal degradation of levoglucosan (1,6-anhydro-beta-D-glucopyranose) was shown to be substantially suppressed in the presence of some aromatic compounds under the conditions of N2/240-340 degrees C/15 min. This stabilization effect is also discussed with CH-pi interaction between levoglucosan and pi-electrons in the benzene ring.
Article
Full-text available
(E)‐4‐O‐Acetyl coniferyl alcohol was synthesized by the reduction of (E)‐4‐O‐acetyl ferulic acid with sodium borohydride and N,N‐dimethylchloromethylenium chloride in 80.2% yield. The glycosylation of (E)‐4‐O‐acetyl coniferyl alcohol with trichloroacetimidoyl 2,3,4,6‐tetra‐O‐pivaloyl‐α‐D‐glucopyranoside in the presence of BF3-Et2O in anhydrous CH2C...
Article
Pyrolysis behavior of wood at gasification temperature (800 °C) was investigated focusing on the behaviors of the wood constituent polymers [cellulose, hemicellulose (glucomannan and xylan) and lignin (milled wood lignin)]. Tar compositions (iso-propanol-soluble and water-soluble tar fractions), which were characterized with GPC, GC–MS, GC-FID (oxi...
Article
Oxime-trimethylsilylation (TMS) method was applied to the analysis of wood pyrolysate. Quantitative determination of hydroxycarbonyls such as glycolaldehyde, which are important pyrolysis products of wood polysaccharide, is difficult as indicated by the gas chromatography–mass spectrometry (GC–MS) and 1H NMR analysis of glycolaldehyde. Glycolaldehy...